diff --git a/kernel/classes/ezstaticcache.php b/kernel/classes/ezstaticcache.php
index 3bd72cb9641..1ca664cc8bc 100644
--- a/kernel/classes/ezstaticcache.php
+++ b/kernel/classes/ezstaticcache.php
@@ -26,7 +26,7 @@
  *
  * @package kernel
  */
-class eZStaticCache
+class eZStaticCache implements ezpStaticCache
 {
     /**
      * User-Agent string